ARM Unveils “Big.Little Processing”: Cortex-A7 and Cortex-A15 in One Chip

ARM on Wednesday announced the ARM Cortex-A7 MPCore processor, the technology that is claimed to be the most energy-efficient application class processor ARM has ever developed. The Cortex-A7 is powered by technologies behind the popular Cortex-A8 that is at the heart of many of today’s most popular smartphones as well as innovations of Cortex-A15.

“The introduction of Cortex-A7 and big.Little addresses this challenge and extends ARM’s technology leadership by setting a new standard for energy-efficient processors and redefining the traditional power and performance relationship,” said Mike Inglis, executive vice president of processor division at ARM.

A single Cortex-A7 processor delivers 5x the energy-efficiency and is one fifth the size of the Cortex-A8 processor, while providing significantly greater performance at lower cost. . The Cortex-A7 processor occupies less than 0.5mm2, using 28nm process technology, and provides compelling performance in both single and multicore configurations. Used as a stand-alone processor, the Cortex-A7 will deliver sub-$100 entry level smartphones in the 2013-2014 timeframe with an equivalent level of processing performance to today’s $500 high-end smartphones.

One of today’s technology most significant challenges is how to create a system-on-chip (SoC) that meets the conflicting consumer demand for devices with both higher-performance and extended battery life. ARM’s Big.Little processing approach, enabled by Cortex-A7, achieves this by pairing the best of the high-performance Cortex-A15 MPCore and ultra-efficient Cortex-A7 processors. Big.Little processing combines two different, but compatible processors within the same SoC and allows the power management software to seamlessly select the right processor, or multiple processors, for the right task. The processors appear identical from an applications software perspective. The ‘Little’, lowest-power processor – in this case, the Cortex-A7 - runs the operating system (OS) and applications for basic always-on, always connected tasks, such as social media and audio playback. The OS and apps can then be seamlessly migrated to the higher-performance processor as demands increase for high end tasks, such as navigation and gaming. The time for this migration is in the order of 20 microseconds.

The efficient and seamless switching of workloads between the two processors is supported by advanced ARM system IP, such as AMBA 4 ACE coherency extensions. This ensures full cache, I/O and processor-to-processor coherency between the Cortex-A15 and Cortex-A7, and across the complete system. Software and applications can therefore continue to run unhindered, and unnoticed by the user, as the tasks are rebalanced to provide the optimum big.LITTLE user experience.